In mobile communication systems, base stations are important components used for connecting User terminals to Base Station Controllers (BSC), receiving and transmitting radio signals between the User terminals and the BSCs, thereby conducting User terminals to access wireless networks and simultaneously accomplishing information intercommunications between User terminals and the BSCs. As shown in FIG. 1, a base station includes:
a Base Station &BSC interface unit, also called transmission unit, used for accomplishing interface functions between the base station and the BSC; a Main Processing & Timing unit, on the one hand, for controlling the base station and exchanging cell and traffic data among the units in the base station, on the other hand, for providing clock signals for other units in the base station; an uplink/downlink base band signal processing unit, used for processing symbol-level and chip-level digital signals in physical layer and communicating digital base band signals with an Intermediate Frequency (IF) signal processing unit; the IF signal processing unit, used for converting digital base band signals to IF signals or converting IF signals to digital base band signals; a power amplifier unit and a duplexer, used for amplifying the IF signals from the IF signal processing unit or an antenna.
In the base station, the Base Station &BSC interface unit, the Main Processing & Timing unit, and the uplink/downlink base band signal processing unit compose a base band part, while the IF signal processing unit, the power amplifier unit and the duplexer compose a Radio Frequency (RF) part which accomplishes conversion between digital base band signals and IF signals, and transmits the processed RF signals. The components in FIG. 1 are all placed in one cabinet to form a complete Base Station.
In traditional base station systems, macro base stations and mini base stations are generally used. A macro base station generally has large capacity so as to support the configuration of as many as 3 or 6 sectors, and includes an indoor type and an outdoor type; while a mini base station usually has small capacity so as to only support the configuration of 1 to 3 sectors. The Mini base station is generally required to have support capability of outdoor application, and acts as a strong complement for the macro base station networking.
The macro base station supports large capacity, and all its single boards and modules are all placed in one cabinet, and thus the macro base station has a large size and a heavy weight, therefore, it needs a special installation room or an outdoor installation base. While the mini base station supports small capacity, the size thereof is comparatively small and it supports pole installation or wall installation, so that the installation is easy and does not need special installation space or floorage. The construction of the macro base station and the mini base station generally used are introduced hereinafter respectively:
(1) In the macro base station, the transmission unit, the Main Processing & Timing unit and the uplink/downlink base band signal processing unit forming the base band part are respectively placed on different functional single boards, which are connected with one another by a backboard. Different single boards or modules may be added according to different capacity expansion requirements; the duplexer, the power amplifier unit, the IF signal processing unit that form the RF part are also placed on different functional single boards, which are connected with each other by a backboard or external wirings. All the above units are configured in one indoor or outdoor cabinet. An outdoor cabinet additionally includes such functional units as temperature control equipment, power supply, environment monitoring equipment and transmission equipment. With all the components in large sizes, the cabinet is very large and heavy, resulting in high cost of transportation and installation and a hard installation site selection, thereby, the network construction speed is badly affected. This kind of structure takes up a large space and leads to a high power consumption and cost. When backup is required, it needs to add some single boards or modules to achieve backup, thereby resulting in high backup cost and complicating backup action.
(2) In the mini base station, all the units in FIG. 1 are placed in a compact structural member module, thereby a mini base station having a small size and an easy installation. A mini base station generally supports configuration of 1-3 sectors. In the situation that one single cabinet supports one sector, a plurality of mini base stations are necessary for networking when more sectors should be supported or large capacity configuration is needed, thereby complicating networking and management of the system.
The mini base station has the shortcomings of small capacity, inconvenient capacity expansion and inflexible networking, although the mini base station has such advantages as small size and easy installation. A plurality of cabinets of mini base stations should be combined when capacity expansion is required, and this is not in favor of wiring, protection and backup. Therefore, mini base stations are not fit for the expected applications of large capacity, furthermore, are not in favor of expanding capacity of the base band part or the RF part respectively due to the base band part and the RF part adopting integration design.